w w w . e l s e v i e r . c o m / l o c a t e / b j i d
The
Brazilian
Journal
of
INFECTIOUS
DISEASES
Original
article
Antiretroviral
drugs
saquinavir
and
ritonavir
reduce
inhibitory
concentration
values
of
itraconazole
against
Histoplasma
capsulatum
strains
in
vitro
Raimunda
Sâmia
Nogueira
Brilhante
a,b,∗,
Érica
Pacheco
Caetano
a,
Giovanna
Barbosa
Riello
a,
Glaucia
Morgana
de
Melo
Guedes
a,
Débora
de
Souza
Collares
Maia
Castelo-Branco
a,b,
Maria
Auxiliadora
Bezerra
Fechine
b,
Jonathas
Sales
de
Oliveira
a,
Zoilo
Pires
de
Camargo
e,
Jacó
Ricarte
Lima
de
Mesquita
f,
André
Jalles
Monteiro
d,
Rossana
de
Aguiar
Cordeiro
a,b,
Marcos
Fábio
Gadelha
Rocha
a,c,
José
Júlio
Costa
Sidrim
a,baSpecializedMedicalMycologyCenter,PostgraduatePrograminMedicalMicrobiology,UniversidadeFederaldoCeará(UFC),Fortaleza,
CE,Brazil
bPostgraduatePrograminMedicalSciences,UniversidadeFederaldoCeará(UFC),Fortaleza,CE,Brazil
cPostgraduatePrograminVeterinarySciences,UniversidadeEstadualdoCeará(UECE),Fortaleza,CE,Brazil
dDepartmentofStatisticsandAppliedMathematics,UniversidadeFederaldoCeará(UFC),Fortaleza,CE,Brazil
eDepartmentofMicrobiology,ImmunologyandParasitology,UniversidadeFederaldeSãoPaulo(UNIFESP),SãoPaulo,SP,Brazil
fHospitalSãoJosé,Fortaleza,CE,Brazil
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received25February2015 Accepted25November2015 Availableonline31December2015
Keywords:
Histoplasmacapsulatum
Saquinavir Ritonavir Itraconazole
a
b
s
t
r
a
c
t
Recent studieshaveshownthatsomedrugsthatarenotroutinelyusedtotreatfungal infectionshaveantifungalactivity,suchasproteaseinhibitorantiretroviraldrugs.Thisstudy investigatedtheinvitrosusceptibilityofHistoplasmacapsulatumvar.capsulatumtosaquinavir andritonavir,anditscombinationwiththeantifungalitraconazole.Thesusceptibilityassay was performedaccordingtoClinical and LaboratoryStandardsInstituteguidelines. All strainswereinhibitedbytheproteaseinhibitorantiretroviraldrugs.Saquinavirshowed min-imuminhibitoryconcentrationsrangingfrom0.125to1gmL−1forbothphases,and
riton-avirpresentedminimuminhibitoryconcentrationsrangingfrom0.0312to4gmL−1and
from0.0625to1gmL−1forfilamentousandyeastphase,respectively.Concerningthe
anti-fungalitraconazole,theminimuminhibitoryconcentrationvaluesrangedfrom0.0019to 0.125gmL−1andfrom0.0039to0.0312gmL−1forthefilamentousandyeastphase,
respec-tively.Thecombinationofsaquinavirorritonavirwithitraconazolewassynergisticagainst
H.capsulatum,withasignificantreductionintheminimuminhibitoryconcentrationsofboth drugsagainstthestrains(p<0.05).Thesedatashowanimportantinvitrosynergybetween proteaseinhibitorsanditraconazoleagainstthefungusH.capsulatum.
©2016PublishedbyElsevierEditoraLtda.ThisisanopenaccessarticleundertheCC BY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
∗ Correspondingauthor.
E-mailaddress:brilhante@ufc.br(R.S.N.Brilhante).
http://dx.doi.org/10.1016/j.bjid.2015.11.003
Introduction
Histoplasmosisisasystemicinfectioncausedbythe dimor-phic fungusHistoplasmacapsulatum. Itismainly associated withimmunosuppression,especiallyinHIVpatients.1,2 This
disease is characterized by a broad spectrum of clinical manifestations ranging from asymptomatic to dissemi-natedforms.3 Histoplasmosisis iswidelydistributed inthe
Americas.4 InBrazil,thenumber ofcaseshasincreasedin
severalregions. Someoutbreakshavebeen recordedinthe country,involvingthestatesofRiodeJaneiro,SãoPaulo,Minas Gerais,EspíritoSanto,MatoGrosso,andRioGrandedoSul.4–6
InCearástate,arecentstudyreported254casesof histoplas-mosisinpatientswithHIVintheperiodfrom2006to2010, showingitshighprevalenceinthisregion.7
Treatmentofhistoplasmosis dependson theseverity of infection,clinicalmanifestationsandindividualriskfactors. The therapy indicated for mild to moderate cases is the administration ofazoles, such as itraconazole. Theuse of amphotericinBislimitedtoseverecasesbecauseofitshigh toxicity.Duetotheincreaseofhistoplasmosiscasesinrecent years,particularlyamongHIVpatients,associatedwiththe occurrence of refractory and recurrent infections, there is a needto find newtherapeutic approaches to controlthis mycosis.8,9Somestudieshaveshownthatcertaindrugsnot
routinelyusedtotreatfungalinfectionshavesignificant anti-fungalactivity.10Amongthese,theantiretroviraldrugshave
demonstratedtheabilitytointerferewiththeviabilityand vir-ulenceoffungalcells.Theproteaseinhibitorsindinavirand ritonavir haveshown in vitro and in vivo inhibitoryeffects againstCandidaalbicans.11Indinaviralsohasshownactivity againstthefungusCryptococcusneoformans,reducingits viru-lenceandmakingitmoresusceptibletothekillingactivityof naturaleffectorcellsoftheimmunesystem.12
Thus,thisstudyaimedtoevaluatetheinvitro susceptibil-ityofH.capsulatumvar.capsulatumtotheantiretroviraldrugs saquinavirandritonavir,aswellastheircombinationwiththe azoleantifungalitraconazole.
Materials
and
methods
Microorganisms
Weusedatotalof20clinicalstrainsofH.capsulatuminthe fil-amentousphaseand10intheyeastphase,isolatedfromthe NortheastandSoutheastregionsofBrazil.Thesamplescame fromtheculturecollectionoftheSpecializedMedical Mycol-ogyCenter,FederalUniversityofCeará,andwerehandledin abiosafetylevel3cabin.
Antifungalagents
Stocksolutionsoftheantiretroviraldrugssaquinavir(Roche HoldingAG,Basel,Switzerland)andritonavir(Abbott Labora-tories,Chicago,USA)andtheantifungalitraconazole(Janssen Pharmaceutica,Beerse,Belgium)werepreparedindimethyl sulfoxide (DMSO). These solutions were stored at −20◦C
untiluse. Serialdilutions ofeach antimicrobialagentwere
preparedinRPMI1640(SigmaChemicalCorporation,St.Louis, MO,USA),supplementedwithl-glutamine,bufferedatapH
of7.0withMOPS165mmoll−1(SigmaChemicalCorporation,
St.Louis,MO,USA).
Preparationoffungalinoculum
Topreparetheinoculum,fungalsuspensionswereprepared insalinefromstockculturesaftersevendaysofincubation, maintainedonBHI(brainheartinfusion)agarandincubated at28◦Cforthefilamentousphase.Thecultureswere
main-tainedonBHIagarsupplementedwithsheepbloodat10%and incubated at35◦Ctoobtain theyeastphase.Theinoculum
wasadjustedto90–95%bytransmittancespectrophotometry at awavelength of530nm. After reading,the suspensions werediluted1:10inRPMI1640mediumtoobtaininoculums ofapproximately0.5×103to2.5×104cfumL−1.13
Susceptibilitytest
The in vitro antifungal activity was determined by the broth microdilution method in accordance with the pro-tocol described in document M27-A3 and standardized by the Clinical Laboratory Standards Institute.14 Initially, the
minimum inhibitory concentration (MIC) was determined for each drug. Subsequently, the MIC values were used as the highest concentration to prepare drugs in com-bination. The concentration ranges of the drugs alone were: 0.0039–2gmL−1 forsaquinavir, 0.0156–8gmL−1 for
ritonavir, and 0.0009–0.5gmL−1 foritraconazole. The
con-centration ranges of the drugs in combination were: 0.0002–1gmL−1forsaquinavir,0.00006–4gmL−1for
riton-avirand0.000003–0.0625gmL−1foritraconazole.Theresults
were determined by visual readings after seven and four daysofincubationat35◦Cforstrainsinthefilamentousand
yeastphase,respectively.TheMICsweredefinedasthe low-est concentration ofdrugableto inhibit80% ofthe fungal growth forantiretroviral drugsand itraconazole,as wellas forthecombinationofboth.13Druginteractionwasevaluated
bycalculating the fractional inhibitoryconcentrationindex (FICI),whichwasclassifiedassynergistic(FICI≤0.5),
indiffer-ent(0.5<FICI<4),orantagonistic(FICI≥4).15TheFICIvalues
obtained for each drug combination against H. capsulatum
were comparedthroughWilcoxontest(p<0.05).The analy-sis wascarried out usingIBMSPSS ver. 21.0software (IBM Co.,Armonk,NY,USA).StandardstrainsofCandida parapsilo-sisATCC22019andCandidakruseiATCC6258wereincludedin eachtestasqualitycontrols.
Results
Theproteaseinhibitorssaquinavirandritonavirwere capa-bleofinhibitingthestrainsofH.capsulatum,withMICvalues rangingfrom 0.125to1gmL−1 forsaquinavirinboth
fila-mentousandyeastphase;andfrom0.0312to4gmL−1and
from0.0625to1gmL−1forritonavirinfilamentousandyeast
Table1–MICsofantiretroviraldrugsanditraconazoleagainststrainsofHistoplasmacapsulatumvar.capsulatumin yeast-likeandmycelialforms.
Strains Saquinavi(gmL−1) Ritonavir(gmL−1) Itraconazole(gmL−1)
Mycelialform
0.125(2)a 0.0312(1) 0.0019(2)
0.25(6) 0.125(1) 0.0078(4)
0.5(8) 0.5(4) 0.0156(6)
1(4) 1(5) 0.0312(6)
2(5) 0.0625(2)
4(4)
Yeastform
0.125(3) 0.0625(4) 0.0039(1)
0.25(1) 0.125(3) 0.0078(4)
0.5(4) 0.5(2) 0.0156(2)
1(2) 1(1) 0.0312(3)
a Numberoftestedstrains.
0.0312gmL−1 forthefilamentousandyeastphase,
respec-tively(Table1).
Synergistic interactions were observed for the combi-nations of saquinavir or ritonavir with itraconazole, and therewasasignificantreductionintheMICofthesedrugs: saquinavir (p=0.0000) and itraconazole (p=0.0000) for fila-mentous and yeast phases; and ritonavir (p=0.0001) and itraconazole (p=0.0003) for filamentous phase and riton-avir(p=0.0297)anditraconazole (p=0.0015) foryeastphase (Table2).Noantagonisticinteractionswereobserved.
Discussion
Inrecentyears,studieshaveshownthatHIVpatientscanhave substantiallylongerlifeexpectancy,dependingonadherence toantiretroviraltreatmentandtheevolutionoftheimmune status.Also,theuseofmoreeffectivetherapydecreasesthe incidenceofopportunisticinfections,including histoplasmo-sis. Even though the use of protease inhibitors, including saquinavir, has been associated with the development of severalsideeffects, recent studieshavedemonstrated that the use of liposome saquinavir formulations significantly decreases the levels of cytotoxicity, besides improving the bioavailabilityofthisdrug.16
Moreover,ithasbeenobservedthattheproteaseinhibitors canhavebeneficialeffectsonsomefungalinfections,notonly bymodulatingthe immunesystemofthe susceptiblehost, butalsobyexertingdirectactionagainstthepathogen.17 It
hasalsobeenobservedfrominvitroandinvivostudiesthat proteaseinhibitorsreducethepathogenicityandgrowthofC. albicansprobablybecausethesedrugsactdirectlyonthe pro-ductionoftheenzymeaspartyl-proteinases,whichissecreted bythisorganismintheprocessesofinvasionandcolonization ofhosttissues.18–20Additionally,ithasbeenshownthat
riton-avir inhibitstheinvitrohyphalgrowth rateofC.albicans,21
ritonavirandsaquinavirinhibittheadherenceofC.albicans
toendothelialcells,22andsaquinavir,ritonavir,andindinavir
attenuatetheinvitroadherenceofC.albicanstoacrylic sub-stances,whichisacommoncomponentoforalappliances.23
Morerecently,itwasobservedthattheproteaseinhibitors saquinavir,darunavir,ritonavir,andindinavirdidnotreduce theinvitrogrowthofC.neoformans,butreducedprotease activ-ityaswellascapsuleproduction,importantvirulencefactors ofC.neoformans.24 Althoughthereare somestudieson the
actionofproteaseinhibitorsagainstfungi,noreportsforH. capsulatumhavebeenpublishedsofar.
In the present study, we observed that the protease inhibitorssaquinavirandritonaviraloneinhibitedH. capsu-latum,andsaquinavirandritonavirinteractedsynergistically withitraconazole,asevidencedbytheincreasedinvitro activ-ityoftheantifungaldrug.Theadvantageofthe synergistic effect of the combination of antiretroviral and antifungal drugsaimstoattenuatetoxiceffectscausedbythem, espe-ciallyincasesoflong-termtherapies,suchasinHIV-infected patientspresentingwithhistoplasmosis.2
Casolarietal.25foundthatsaquinaviralonedidnotshow
significant antifungalactivity againstthe yeastformsofC.
Table2–EffectsofthecombinationofantiretroviraldrugsanditraconazoleonstrainsofH.capsulatumvar.capsulatumin yeast-likeandmycelialforms.
Strains Drugs MIC–geometricmean (isolateddrugs)
MIC–geometricmean (combineddrugs)
FICIgeometric mean
Results Numberofstrains presentingsynergism
Antiretroviral Antifungal Antiretroviral Antifungal
Mycelial form
SAQ/ITC 0.4 0.01 0.002 0.0001 0.007 S 20/20
RIT/ITC 1.03 0.01 0.27 0.004 0.5 S 13/20
Yeast form
SAQ/ITC 0.45 0.01 0.02 0.001 0.12 S 10/10
RIT/ITC 0.15 0.01 0.01 0.001 0.16 S 10/10
albicansandC.neoformans.However,whencombinedwiththe azoledrugfluconazole,itwasfoundtoinhibitthegrowthof thesefungalspecies,indicatingtheoccurrenceofsynergism betweenthedrugs.Similarly,Palmeiraetal.26describedthe
effectofnelfinavirandsaquinaviragainstthedematious fun-gusFonsecaeapedrosoiandconfirmedthatthesecompounds alone were unable to inhibit the growth of this fungus. However,inhibitiondidoccurwhensub-inhibitorydosesof theseproteaseinhibitorswerecombinedwithamphotericin B.Mikusetal.27notedthatritonavirprolongstheclearanceof
voriconazole,althoughtheuseofritonavirwithvoriconazole is contraindicated because the former lowers the plasma levelsofvoriconazole.
Ourdatademonstratedaninvitrosynergisticinteraction betweensaquinavirorritonavirwithitraconazoleagainstthe dimorphicfungusH.capsulatum.Themechanismunderlying theobservedsynergyremainsunknown,butCrommentuyn etal.28showedthattheinvivocombinationofantiretroviral
lopinavir/ritonaviranditraconazole interactsthrough phar-macokineticpathways,interferingwiththemetabolismofthe antifungaldrug,whichincreasestheplasmalevelofthe anti-fungalagent,thus,makingitpossibletoreducethedosageof itraconazolewithoutimpairingthetreatment.Basedonour findings,webelievethatsaquinavirorritonavirwith itracona-zoleinteractprobablythroughpharmacodynamicpathways.
Thesedata showan importantinvitrosynergy between saquinavirorritonaviranditraconazoleagainstthefungusH. capsulatum,whichisanimportantpathogenforAIDSpatients.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
Acknowledgments
ThisresearchwassupportedbyCNPqprocess(303396/2014-8; 552161/2011-0)andCAPES(AE1–0052-000630100/11).
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